Solar power material converts 90 per cent of light into heat

Researchers have developed a new nanoparticle-based material for concentrating solar power plants that can absorb and convert to heat more than 90 per cent of the sunlight it captures.

The new material can also withstand temperatures greater than 700 degrees Celsius and survive many years outdoors in spite of exposure to air and humidity.

By contrast, current solar absorber material functions at lower temperatures and needs to be overhauled almost every year for high temperature operations.

“We wanted to create a material that absorbs sunlight that doesn’t let any of it escape. We want the black hole of sunlight,” said Sungho Jin, a professor in the department of Mechanical and Aerospace Engineering at the University of California, San Diego Jacobs School of Engineering.

Jin, along with professor Zhaowei Liu of the department of Electrical and Computer Engineering, and Mechanical Engineering professor Renkun Chen, developed the Silicon boride-coated nanoshell material.

The novel material features a “multiscale” surface created by using particles of many sizes ranging from 10 nanometres to 10 micrometres.

The multiscale structures can trap and absorb light which contributes to the material’s high efficiency when operated at higher temperatures.

Traditional power plants burn coal or fossil fuels to create heat that evaporates water into steam.

The steam turns a giant turbine that generates electricity from spinning magnets and conductor wire coils.

Concentrating solar power plants create the steam needed to turn the turbine by using sunlight to heat molten salt.

The molten salt can also be stored in thermal storage tanks overnight where it can continue to generate steam and electricity, 24 hours a day if desired, a significant advantage over photovoltaic systems that stop producing energy with the sunset.

One of the most common types of CSP systems uses more than 100,000 reflective mirrors to aim sunlight at a tower that has been spray painted with a light absorbing black paint material.

The material is designed to maximise sunlight absorption and minimise the loss of light that would naturally emit from the surface in the form of infrared radiation.

The UC San Diego team developed, optimised and characterised a new material for this type of system over the past three years.

The synthesised nanoshell material was spray-painted in Chen’s lab onto a metal substrate for thermal and mechanical testing.

The material’s ability to absorb sunlight was measured in Liu’s optics laboratory using a unique set of instruments that takes spectral measurements from visible light to infrared.